This invention relates, in general, to electronics, and more particularly, to sensors and methods of use.
Micromachined sensors can detect acceleration by measuring a change in capacitance. Many sensors are in-plane sensors that detect acceleration along an axis parallel to the surface of a support substrate. These in-plane sensors have an electrode that overlies the surface of the support substrate where the electrode moves along the axis in response to an acceleration along that same axis. The electrode moves between two stationary electrodes, and the differential capacitance between the two stationary electrodes and the movable electrode determines the magnitude of acceleration.
However, these in-plane sensors are also mobile along an orthogonal axis that is perpendicular to the surface of the underlying support substrate. A large acceleration force along the orthogonal axis could move the movable electrode on top of one of the two stationary electrodes, and the movable electrode could remain immobilized in that position. This immobilization makes the sensor inoperable.
Additionally, the in-plane sensors also have stiction problems that affect the manufacturing yields of the sensor and that also affect the reliability of the sensor. During manufacturing, stiction may prevent the movable electrode from becoming mobile. During use, stiction may convert a previously movable electrode into an immobile electrode. Both of these results render the sensor inoperable.
Accordingly, a need exists for an improved sensor and method of use that improves the manufacturing yields of the sensor and the reliability of the sensor.